1. Field of the Invention
The invention is related to a transmission system comprising a transmitter for transmitting a sequence of words comprising digital symbols via a transmission medium to a receiver, said receiver comprises means for recovering words comprising digital symbols from said sequence. The invention is also related to a receiver, an arrangement and a method to be used in relation with the above mentioned transmission system.
2. Description of the Related Art
A transmission system according to the preamble is known from U.S. Pat. No. 4,955,037.
Such transmission system can e.g. be applied for the transmission of audio or video signals in digital form via the public telephone network, or for the transmission of such signals in mobile radio systems. Said transmission systems can also be used for the recording and reproduction of digital symbols using magnetic tapes or magnetic discs such as hard discs or floppy discs. Said transmission system can also be used with optical or opto-magnetic discs.
In order to transmit signals in digital form, often words of digital symbols are formed, which words have to be transmitted via the transmission medium or have to be recorded on a recording medium. The words of digital symbols are generally transmitted/recorded in serial form on the respective medium.
In order to recover the words of digital symbols the position of the word boundaries in the received sequence has to be found. A first method to enable recovery of the words from the sequence, is to introduce synchronisation words in the sequence of words. These synchronisation words are formed by a unique string of symbols. By analyzing the received sequence, and determining the position of the synchronisation words, the boundaries between all words in the sequence of digital symbols are known. A disadvantage of using synchronisation words is the loss of transmission capacity, because synchronisation words do not carry any payload data.
In the transmission system according to the above mentioned U.S. patent no. synchronisation words are used. For determining the boundaries between words in the sequence, a probability measure of 16 predetermined strings of digital symbols is determined as function of the value of said strings. This is done for each of a plurality of positions (8) of said 16 strings in the sequence. The correct position of the words of digital symbols is derived from the position in which the probability measure of said 16 strings approximates a predetermined function. In this way the statistical properties of the sequence of digital symbols are exploited to find the correct boundaries between the words.
The determination of the probability measures of 16 strings for 8 positions, requires a substantial amount of processing power, which leads to high costs of the transmission system.